Device for the reversed-phase separation and on-target deposition of peptides incorporating a hydrophobic sample barrier for matrix-assisted laser desorption/ionization mass spectrometry

The separation of peptide mixtures from proteolytic cleavage is often necessary prior to mass spectrometry (MS) to enhance sensitivity and peptide mapping coverage. When buffers, salts, and other higher abundance peptides/contaminants are present, competition for charge during the electrospray ionization and matrix-assisted laser desorption/ionization (MALDI) processes can lead to ion suppression for the targeted analyte(s). In this note, a simple reversed-phase microcolumn sample separation and deposition device (Sep-Dep) is described. The use of this device improves or renders possible the analysis of complex or contaminated peptide mixtures by MALDI-MS. The method is simple and inexpensive and utilizes single-use low-cost Geloader-type columns packed with reversed-phase material. The device described utilizes an open column, allowing for a gradient or narrow-step gradient to be applied by any solvent delivery system or manually with a pipet. A key feature of the device is a deposition chamber that can be custom-built to hold any MALDI target. The Sep-Dep device is attached directly to an in-house vacuum line and draws solvent from the open-ended LC column. The elution of separated peptides is performed directly onto a target that has been treated with a hydrophobic barrier. This barrier effectively isolates fractions and improves the quality and morphology of the matrix crystals. The method produces efficient separations of proteolytic peptides, significantly reducing signal suppression effects in MALDI.     

Resistance Compression Networks for Radio-Frequency Power Conversion

A limitation of many high-frequency resonant inverter topologies is their high sensitivity to loading conditions. This paper introduces a new class of matching networks that greatly reduces the load sensitivity of resonant inverters and radio frequency (RF) power amplifiers. These networks, which we term resistance compression networks, serve to substantially decrease the variation in effective resistance seen by a tuned RF inverter as loading conditions change. We explore the operation, performance characteristics, and design of these networks, and present experimental results demonstrating their performance. Their combination with rectifiers to form RF-to-dc converters having narrow-range resistive input characteristics is also treated. The application of resistance compression in resonant power conversion is demonstrated in a dc-dc power converter operating at 100MHz     

Design and experimental implementation of an electromagnetic engine valve drive

In conventional internal combustion engines, engine valve displacements are fixed relative to crankshaft position. If these valves were actuated as a variable function of crankshaft angle, significant improvements in fuel economy could be achieved. To this end, a new type of electromagnetic valve drive system (EMVD) for internal combustion engines was more recently proposed. This EMVD incorporates a disk cam with a very desirable nonlinear profile which that functions as a nonlinear mechanical transformer. Modeling and simulation results showed significant advantages of this EMVD over previously designed electromagnetic engine valve drives. In this articles, we describe an experimental implementation of the proposed EMVD, which was developed to confirm these benefits. The EMVD apparatus was designed, constructed, and integrated into a computer-controlled experimental test stand. The experimental results confirm the benefits of using a nonlinear mechanical transformer in a motordriven engine-valve spring system, as seen in the small average power consumption and low valve seating velocity. In addition, a valve transition time sufficient for 6000-rpm engine operation was achieved. The results also suggest ways to improve the EMVD apparatus in the future.     

Comparative study of two methods used for the characterization of the degradation of the polymer binder in gap-based propellants

Abstract

Reliability assessment for composite propellants calls for effective shelf-life predicting tools, implying the existence of appropriate accelerated-aging procedures and of quantitative methods for the characterization of the degradation process. Ideally, one would like to investigate stabilizer depletion as well as the mechanical integrity of the polymer network used as the binder. There are many available methods that can be combined to achieve this goal. In the present work, a comparative study of two of these methods has been performed. The first procedure makes use of FTIR spectroscopy to characterize the binder's degradation and of HPLC to follow stabilizer depletion. The other method, based on ¹H NMR spectroscopy allows the measurement of the polymer network degradation, the depletion of the stabilizer and the loss of plasticizer in a single step. Finally, the pros and cons of both procedures have been evaluated from the analysis of experimental data related to accelerated aging at 40, 60 and 80°C of GAP-based composite propellant formulations.     

Lymphoma cell burden in progenitor cell grafts measured by competitive polymerase chain reaction: less than one log difference between bone marrow and peripheral blood sources

The suppressor of Hairy-wing [SU(HW)] binding region disrupts communication between a large number of enhancers and promoters and protects transgenes from chromosomal position effects. These properties classify the SU(HW) binding region as an insulator. While enhancers are blocked in a general manner, protection from repressors appears to be more variable. In these studies, we address whether repression resulting from the Polycomb group genes can be blocked by the SU(HW) binding region. The effects of this binding region on repression established by an Ultrabithorax Polycomb group Response Element were examined. A transposon carrying two reporter genes, the yellow and white genes, was used so that repression and insulation could be assayed simultaneously. We demonstrate that the SU(HW) binding region is effective at preventing Polycomb group repression. These studies suggest that one role of the su(Hw) protein may be to restrict the range of action of repressors, such as the Polycomb group proteins, throughout the euchromatic regions of the genome.     

Filters with active tuning for power applications

Filters for switched-mode power converters have traditionally relied on low-pass networks-with corner frequencies well below the ripple fundamental-to attenuate switching harmonics over a range of frequencies. The filters explored in this report provide extra attenuation at discrete frequencies, easing the filtering requirement of accompanying low-pass networks. When a converter's switching frequency is tuned to a filter resonance using a novel phase-lock control scheme, a resonant filter can match the ripple-attenuation performance of a low-pass network for less volume, weight, and expense. The design and application of resonant filters and active-tuning control are discussed, and experimental results from the input filter and power stage of a prototype DC-DC converter are presented.     

Computer-aided optimization of DC/DC converters for automotive applications

This paper investigates computer-aided optimization of DC/DC converters, with a focus on converters for dual-voltage automotive electrical systems. A new CAD optimization approach based on Monte Carlo search methods is introduced which allows the design space to be rapidly explored in an automated fashion and the most optimal designs and design approaches to be identified. The optimization approach also allows the effects of variations in design specifications on the cost, weight, and volume of an optimized converter to be readily determined. A prototype converter designed using this optimization procedure is evaluated and compared to a converter designed by conventional means.     

Efficacy and costs of patient-controlled analgesia versus regularly administered intramuscular opioid therapy

BACKGROUND: Many studies have shown the efficacy of patient-controlled analgesia (PCA). However, it is not clear whether PCA has clinical or economic benefits in addition to efficient analgesia. The current study was designed to evaluate these issues by comparing PCA with regularly administered intramuscular injections of opioids after hysterectomy. METHODS: This prospective study included 126 patients who underwent abdominal hysterectomy and were randomly assigned to receive PCA or regularly timed intramuscular injections of morphine during a period of 48 h. Doses were adjusted to provide satisfactory analgesia in both treatment groups. Pain at rest and with movement, functional recovery, drug side effects, and patient satisfaction were measured using rating scales and questionnaires. The costs of PCA and intramuscular therapy were calculated based on personnel time and drug and material requirements. RESULTS: Comparable analgesia was observed with the two treatment methods, with no significant differences in the incidence of side effects or patient satisfaction. The medication dosage had to be adjusted significantly more frequently in the intramuscular group than in the PCA patients. The PCA did not favor a faster recuperation time compared with intramuscular therapy in terms of times to ambulation, resumption of liquid and solid diet, passage of bowel gas, or hospital discharge. The results of the economic evaluation, which used a cost-minimization model and sensitivity analyses, showed that PCA was more costly than regular intramuscular injections despite the fact that no costs for the pump were included in the analyses. Cost differences in nursing time favoring PCA were offset by drug and material costs associated with this type of treatment. CONCLUSIONS: Compared with regularly scheduled intramuscular dosing, PCA is more costly and does not have clinical advantages for pain management after hysterectomy. Because of the comparable outcomes, the general use of PCA in similar patients should be questioned.     

Development of a highly polymorphic STR marker for identity testing purposes at the human androgen receptor gene (HUMARA)

We developed a non-isotopic method which improves the technical quality of the X-linked HUMARA locus typing process. The use of formamide and a low concentration of acrylamide increased resolution and sharpness of HUMARA alleles in silver-stained polyacrylamide gels. In addition, the construction of an allelic ladder containing amplified sequence of 9 alleles (even-numbered alleles) of the HUMARA locus, allows confident, rapid and precise assignment of discretely defined alleles. Allele and genotype frequencies for the HUMARA locus were determined in a French Canadian population sample. Observed genotype frequencies in females conformed to Hardy-Weinberg expectations. Furthermore, the HUMARA locus is highly polymorphic with 18 observed alleles and an heterozygosity value of 89.3%. Also, this locus has average powers of discrimination of 97.8% and 88.7% for testing samples of female and male origin, respectively. In the French Canadian population, the average probability of excluding a random man as the father in paternity analysis when both mother and daughter are tested for this locus is 88.0%. Together, the results indicate that the HUMARA locus provides a highly discriminatory system that is appropriate for the purposes of forensic identification and paternity testing involving a female child.